8M0090559 Maintenance Kit for Mercury 40HP 50HP 60HP EFI CT Big Foot | JLM Marine

8M0090559 Maintenance Kit for Mercury 40HP 50HP 60HP EFI CT Big Foot

This comprehensive maintenance kit is engineered for Mercury 40 / 50 / 60 EFI CT & Big Foot 4-Stroke outboard engines. It consolidates essential service components—including impeller, seals, gaskets, thermostat, fuel filters, oil filter, and gear oil pump—into one complete package to simplify routine maintenance and extend engine life.

Direct Replacement for OEM Part Number: 8M0090559. This aftermarket kit meets OEM specifications and provides reliable performance for scheduled service intervals.

• Includes 19 individual components covering water pump, fuel system, lubrication, and cooling service
• Designed specifically for EFI (Electronic Fuel Injection) Command Thrust and Big Foot models
• Complete kit eliminates the need to source parts individually

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This maintenance kit includes the following components:

• 47-43026Q02 (Impeller) × 1 [Essential water pump component]
• 26-8M2014338 (Seal) × 1
• 2210 (Seal) × 1
• 8172761 (Plate) × 1
• 25-21836 (O-ring) × 2
• 27-8M0142616 (Gasket) × 1
• 27-8172771 (Gasket) × 1
• 28-8M0032833 (Key) × 1
• 26-45577 (Seal) × 1
• 25-90196 (O-ring) × 1
• 26-830749 (Gasket) × 3
• 8M0117413 (Thermostat) × 1 [Critical cooling component]
• 27-8M0177107 (Gasket) × 1
• 35-879884T (Fuel filter) × 1
• 35-8M0153652 (Fuel filter) × 1 [Two fuel filters included]
• 35-8M0162829 (Oil filter) × 1
• 8M007119 (Drain Gasket) × 1
• 830749 (Drain Gasket) × 3
• 24OP149 (Gear Oil Pump) × 1

Installation Guide

1. Preparation: Disconnect the battery and allow the engine to cool completely. Gather necessary tools including socket set, screwdrivers, and a drain pan.
2. Oil Change: Remove the drain plug using the included drain gasket (8M007119) and drain the engine oil. Install the new oil filter (35-8M0162829) and refill with manufacturer-recommended oil.
3. Fuel Filters: Locate and replace both fuel filters (35-879884T and 35-8M0153652) in sequence. Ensure fuel lines are properly reconnected and check for leaks.
4. Water Pump Disassembly: Remove the lower unit and locate the water pump housing. Carefully disassemble the pump, noting the orientation of all components.
5. Impeller Replacement: Remove the old impeller and install the new impeller (47-43026Q02) with blades oriented in the correct rotation direction. Apply marine grease to the impeller before installation.
6. Seals & Gaskets: Replace all water pump seals (26-8M2014338, 2210, 26-45577) and gaskets (27-8M0142616, 27-8172771) as you reassemble. Ensure all mating surfaces are clean and free of debris.
7. Plate & Key Installation: Install the plate (8172761) and key (28-8M0032833) in their proper positions within the water pump assembly.
8. O-rings: Replace all O-rings (25-21836 ×2, 25-90196) and the multiple gaskets (26-830749 ×3). Lubricate O-rings with a light coating of marine grease.
9. Thermostat Replacement: Locate the thermostat housing, remove the old thermostat, and install the new thermostat (8M0117413) with its gasket (27-8M0177107). Ensure proper orientation per service manual.
10. Gear Oil Service: Use the included gear oil pump (24OP149) and drain gaskets (830749 ×3) to drain and refill the lower unit with fresh gear oil. Check for proper fill level through the vent hole.
11. Reassembly: Reinstall the lower unit, torquing all fasteners to manufacturer specifications. Double-check all connections and gasket seating.
12. Testing: Reconnect the battery, start the engine in a test tank or on muffs, and verify proper water flow from the telltale. Check for leaks and confirm normal operating temperature.

Troubleshooting & FAQ

Q: How do I confirm this maintenance kit fits my Mercury outboard?
A: Verify your engine is a Mercury 40, 50, or 60 HP EFI (Electronic Fuel Injection) Command Thrust or Big Foot 4-stroke model. Cross-reference your existing part number 8M0090559 or consult your engine's service manual and serial number plate to confirm compatibility before ordering.

Q: How often should I perform this maintenance service?
A: Mercury recommends full maintenance every 100 hours of operation or annually, whichever comes first. In saltwater or heavy-duty conditions, inspect the impeller and filters more frequently—every 50 hours or mid-season.

Q: What are the signs that my water pump impeller needs replacement?
A: Common symptoms include reduced water flow from the telltale (indicator stream), engine overheating, steam from the engine, or an overheating alarm. If you notice any of these, shut down immediately and inspect the impeller and cooling system.

Q: Can I use this kit if I have a standard Mercury 50HP without EFI or Big Foot?
A: No, this kit is specifically designed for EFI Command Thrust and Big Foot models. Standard carbureted or non-CT/Big Foot engines require different components, particularly fuel filters and water pump parts. Always match the kit to your exact engine configuration.

Q: Do I need any additional gaskets or sealants not included in this kit?
A: This kit includes all major service gaskets, seals, and O-rings for the specified maintenance interval. You may want to have marine-grade gasket sealant or RTV silicone on hand for certain applications, but it is not required for most installations if gaskets are properly seated.

Q: Is this an OEM or aftermarket product?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
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